Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 47 for “"Stress wave"”.
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Geopolymer composites and their applications in stress wave mitigation
… and displayed interesting dynamic behavior for stress wave mitigation and as acoustic metamaterials. The fabrication of geopolymer beads was achieved by simple injection into a Polydimethylsiloxane (PDMS) polymer mold. Based on the mechanical properties of geopolymers, the dynamic responses of …
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Nondestructive Evaluation/characterization of Airport Pavements Using Stress Wave Methods
Energy-related processes in engineering systems and materials are numerous and may collectively describe most meaningful mechanical and physical features of the material/system. Those features may be retrieved using single, or ensemble-averaged, impulse-generated NDE tests using the methodology …
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The effect of rope damage on the stress wave factor
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982.
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Stress Wave Scattering in Concrete: An Investigation Through Simple Finite Element Models
… a method to estimate the scattering component of stress wave attenuation in concrete and concretelike materials through the use of simple finite element models in two dimensions. The method employs a correction to account for losses due to normal radiation pattern effects and test setup geometry. …
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Stress Wave Propagation In A ‘Simplified Surrogate Tibia’ Subjected To Blast Loading
… landmine blast scenario. The study of stress wave propagations in the tibia during an anti-vehicle landmine blast aids in scientific understanding of blast injuries produced by anti-vehicle landmines by refining current ideas, discovering novel phenomena, and filling information gaps. …
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Axisymmetric stress wave propagation in weakly coupled layered structures: Analytical and computational studies
Stress wave propagation in layered systems with infinite and finite numbers of isotropic layers is investigated. A transfer matrix formulation for the axisymmetric problem is developed using a double integral transform technique and a symbolic algebra system. The propagation and attenuation zones …
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Relationship of bacterial infection and stress wave travel time in red oak lumber
… project investigated the possibility to use stress wave timing for the identification of bacterial infection, by studying the relationship of the level of bacterial infection and impact-induced stress wave travel time across the grain of green 4/4 red oak lumber from Southcentral Virginia. …
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In-situ assessment of concrete bridge decks and pavements using stress-wave based methods
… critical for its maintenance and rehabilitation. Stress-wave based methods, including ultrasonic surface wave (USW) and impact echo (IE), are becoming popular for characterizing defects and mechanical properties of concrete infrastructures. In this dissertation, a comprehensive literature review …
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Wave management in 1D and 2D granular systems: designs for stress wave mitigation and control
Controlling stress waves during impact beyond merely dissipating their energy through material fracture, fragmentation, yielding etc., has been a significant focus of research in recent years. Materials exhibiting stress wave control characteristics would enable novel applications, such as for …
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Design and fabrication of ceramic beads and laminated composites for the study of stress wave mitigation
Research on theoretical models to study stress wave management has created new opportunities to design and fabricate beads and laminated composites in order to improve the material performance of engineering devices such as armors, casing for sensitive equipment, and heavy machinery. This thesis …
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Measurements of Surface Displacements During Stress Wave Propagation in Opaque Solids Using Pulsed Laser Speckle Photography
… of measuring surface displacements due to stress waves and propagating cracks in solids. A double exposure recording allows the comparison of object points to be made between two states of displacement. The final specklegram is processed and treated as a diffraction grating to yield both …
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An investigation of the influence of grain size on stress wave attenuation and dispersion in rock like materials
<p>"A mathematical model which is independent of any specific physical mechanism and based on two port linear network theory is developed to describe attenuation and dispersion in a medium. The assumption is made that the ll medium behaves in a linear manner. The influence of grain size on …
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A pulsed laser loading technique for controlled dynamic loading of nanostructred materials
… technique for controlling and calibrating the stress waves created from this ultra-high loading rate technique. In the high-power pulsed laser loading technique, a laser produced compressive stress pulse passes through a substrate and reflects at a traction free surface as a tensile wave of …
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Numerical investigation of dispersion in Hopkinson Pressure Bar
… very little attention to the modelling of the stress wave propagation in the cylindrical bars. This dissertation focuses on the numerical modelling of stress wave propagation in HPBs.
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Detection of in-plane stress waves with Polyvinylidene Fluoride (PVDF) sensors
… (PVDF), a piezoelectric polymer, is an excellent stress sensor. The objective of this research is to investigate the application of the PVDF sensors for detection of in-plane stress waves in 31 and 32 modes. This was achieved by focusing on aspects of PVDF sensing related to determination of …
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In situ determination of strength and stiffness of structural lumber and composite products
… of built-in wooden members. Methods included stress wave timing for dynamic MOE determination and screw withdrawal force (SWF) for MOR and density prediction. Standard ASTM testing procedures were used to determine the actual properties and statistical relationships between these variables …
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Acoustic assisted actuation of Ni-Mn-Ga ferromagnetic shape memory alloys
… single crystals of the use of a sinusoidal stress wave generated by a piezoelectric stack actuator. The piezoelectric drive causes a time varying stress wave in the FSMA that resolves as a shear across the twin-boundaries and aids the twin boundary in overcoming defect-related obstacles. The …
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An investigation into the characterisation of the spalling behaviour of Polycrystalline Diamond Compact(PDC) cutters under impact loading conditions
… diamond compact (PDC) cutters and the effect of stress wave shape on the degree of spalling was performed using the split-Hopkinson pressure bar (SHPB) apparatus. The PDC cutters were loaded under specific impact conditions and their reactions monitored and characterised. In order to isolate and …
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Destructive disassembly of bolts and screws using impact
… by studying the characteristics of elastic waves caused by impact. This research presents a new method for increasing the shear stress applied on the bolt head without increasing the energy input invested on launching striker. The equations are developed for the elastic waves in …
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Delamination of Thin Film Patterns Using Laser-Induced Stress Waves
… contact and complex bonding processes. The stress wave generation is highly repeatable, multiple tests can be carried out on a single substrate, and final calculation of the interfacial energy does not require a complex stress analysis. Overall, this experimental methodology offers great …
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